package w1;

import java.util.Scanner;

public class Lt2 {
	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
		System.out.println("输入圆半径：");
		double r = input.nextDouble();
		double area = 3.14 * r * r;
		System.out.printf("area = %f\n", area);
	}
}
